The invention relates to improvements in interlocking flexible plastic fasteners and more particularly to continuous fasteners having interlocking ribs and grooves wherein the fasteners have fluid-tight integrity with the fastener structure providing means for testing the fluid-tight integrity.
Interlocking ribs and grooves which are fluid-tight or leak-proof have heretofore been provided and an example of such structure is shown in U.S. Pat. No. 3,918,131, Steven Ausnit, issued Nov. 11, 1975. Such fasteners are frequently used in environments wherein the fluid-tight nature (either vapor or liquid) is required and leakage cannot be tolerated. This type of fastener is continuous and is conveniently made in substantial quantities by extrusion from polyethylene, PVC, polyurethane or other similar flexible thermoplastic through a die opening shaped in accordance with the shape of the rib and groove. Subsequently the rib and groove are interlocked to provide a fastener having fluid-tight integrity. During the extrusion process and cooling thereafter, small variations in tolerance or surface defects can occur in the rib and groove, so that a source of possible leakage can occur where the ribs and grooves do not fit tightly to each other in surface-to-surface engagement.
In environments where vapor or liquid-tight integrity must be maintained such as in the isolation of chemicals or certain toxic materials, it is critical to be able to test the fastener either before and/or after installation, in order to be assured that the fluid-tight integrity is present. Such testing cannot employ the use of any deleterious materials such as dyes or gases which would damage the fastener or which might use substances which would adhere to the fastener that would adversely affect the material which is being protected. Also, it may be necessary to pressure test the fastener where pressure differences would exist across the fastener in its use. Other examples of uses where the leak-proof integrity of fasteners must be employed are in uses in the construction trade where the fasteners are used to keep out the elements. Fasteners, for example, joining waterproof surfaces, have been used to protect various contents which can be damaged by rain, sleet or snow.
It is accordingly an object of the present invention to provide a flexible fastener which has an improved means for testing its fluid-tight integrity and for easily detecting whether any leaks are present. A further object of the invention is to provide a method and structure for testing the fluid-tight integrity of a rib and groove zipper structure.
A still further object of the invention is to provide a zipper structure wherein the capability of testing for leaks is inherent in the unique structure and where the particular capability is present that the fluid-tightness of the structure can be tested after installation on the site or in the environment in which it is to be used and wherein testing can be re-establishing periodically after installation.
A feature of the invention is the provision of a flexible plastic fastener having spaced interlocking rib and groove elements thereon with a built-in compartment or passageway therebetween adapted to be pressurized by a fluid so that testing of the fastener can be accomplished by pressurizing the compartment and observing leakage. This could be accomplished, for example, by pressurizing the compartment with air and placing the fastener under water to observe if air bubbles occur as a result of leakage between the surfaces of the interlocked rib and groove members of the fastener.
Other objects, advantages and features will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments thereof in the the specification, claims and drawings in which: